1. Technical Field
The present invention relates to a liquid development system which develops a latent image formed on an image carrier member with use of a developing agent, an image forming apparatus using a liquid developing agent, by which transfer is carried out at a transfer position of a primary transfer section from an image carrier member to an intermediate transfer member as well as at a transfer position of a secondary transfer section from the intermediate transfer member to a recording medium, and an image forming method thereof.
2. Related Art
Various proposals have been made for a wet image forming apparatus which develops a latent image with use of a highly viscous liquid developing agent, to visualize the electrostatic latent image, whereby the developing agent contains solid toner formed of solid component and dispersed in a liquid solvent. A developing agent used in this wet image forming apparatus is prepared by suspending solid content (toner particles) in an electric insulating organic solvent (carrier liquid) such as a silicon oil, mineral oil, or edible oil. The toner particles are so micronized as to have a particle diameter of 1 μm or so. Due to use of such micro toner particles in a wet image forming apparatus, relatively high quality can be achieved compared with a dry image forming apparatus using toner powder of particles having a particle diameter of about 7 μm.
A carrier liquid contained in a developing agent functions not only to prevent scattering of toner particles having a particle diameter of 1 μm or so but also to make the toner particles charged and further dispersed uniformly. In developing and transfer process, the carrier liquid also functions to allow the toner particles to easily move due to an electric field effect. Thus, a carrier liquid is a necessary component for toner storing process, toner carrying process, developing process, and transfer process. Quantity of this carrier liquid is desirably adjusted depending on the type of a recording medium when performing, at the transfer position of the secondary transfer section, transfer to a recording medium from the intermediate transfer member. That is, the quantity of carrier liquid at the transfer position of the secondary transfer section is desirably adjusted depending on the type of paper, such as paper having a smooth surface which hardly absorbs a carrier liquid or coated paper having a surface coated thick (coated with a large quantity of coating agent), rough paper having coarse texture like recycled paper which easily absorbs the carrier liquid, ordinary paper which absorbs the carrier liquid at an intermediate absorbent rate between the coated paper and rough paper, etc.
Jpn. Pat. Appln. Laid-Open Publication No. 2003-91161 discloses a method for variably adjusting quantity of carrier to be removed depending on paper types, whereby the quantity of carrier to be removed is adjusted by use of a squeeze roller provided on a latent image carrier member. Specific examples of the method for adjusting quantity of carrier to be removed are an adjustment method by changing a nip width between the squeeze roller and the latent image carrier member, another method by changing a difference in bias between the squeeze roller and the latent image carrier member, and yet another method by changing pressure of a cleaning blade above the squeeze roller.
To adjust quantity of carrier to be removed according to a method as described in the Publication No. 2003-91161, a toner image has to be pressed on a latent image (carrier member) with a physical force or a bias has to be applied on a toner image by electricity (an electric field). This causes developed and visualized thin lines to become fat. Alternatively, a turbulence in an image occurs to collapse open areas or an error is caused in transfer to the intermediate transfer member. Further, in the adjustment method by changing pressure of the cleaning blade above the squeeze roller, toner removed and splashed from non-image areas sticks together, so that the splashing toner causes an image disturbance.